Geomagnetic variation observed at Aso Volcano during the past ten years (1991-2000)

阿蘇中岳火口周辺で1991-2000年に観測された地磁気変化について, 種々の観測量, とりわけ微動および表面活動との対応に注目して考察した。Tanaka(1993)が1980-1990年の活動期に注目して提唱した「熱消帯磁モデル」は, その後も基本的に有効である。微動振幅の増大は, 物質と熱の輸送に深い関係があることが示唆され, 火口直下の温度は, 表層の物理状態に大きな影響を受けることが示された。
We investigated geomagntic changes observed around the active crater of Nakadake, Aso Volcano during the period of 1991-2000 with special attention to tremors and superficial activities of the volcano. The idea of de/re-magnetization due to shallow heat transfer proposed by Tanaka (1993) has been proved to be valid also to the recent data. It has been suggested that an onset of magnetization period frequently coincides with a tremor burst. It is proposed that the condition of the crater bottom severely affects the heat transfer system at shallow part.